Blood perfusion through the capillary bed is the final transport step before nutrients and oxygen diffuse to cells, and the first step for removal of waste products diffusing away from cells. The ability to non-invasively measure perfusion characteristics such as blood volume and velocity is important clinically since perfusion plays a role in many pathologies. Perfusion imaging by intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) was proposed over thirty years ago, however, acceptance of IVIM MRI has lagged due to poor reproducibility of IVIM perfusion metrics. The objective of this project is to approach the problem of poor reproducibility by using porous media nuclear magnetic resonance (NMR) theory to develop IVIM MRI methods that correctly model the types of fluid motions that occur during perfusion. The methods will be optimized on well-defined phantoms to evaluate the ability to measure perfusion characteristics. Then the perfusion imaging methods will be applied to prostate tumors and placentas complicated by preeclampsia. The project is anticipated to have a significant positive impact on the clinical capability and utility of IVIM MRI.